Liquid crystal display having particular reflective area and transmissive area

ABSTRACT

The invention relates to a transflective liquid crystal display capable of display in both of transmissive and reflective modes and a method of manufacturing the same and provides a transflective liquid crystal display which can achieve high display characteristics in both of the transmissive and reflective modes. A configuration is employed which includes a liquid crystal display panel having a pair of substrates and a liquid crystal layer sealed between the substrates, a pixel region including a reflective area having a reflector for reflecting light entering from the side of one of the pair of substrates and a transmissive area for transmitting light entering from the side of the other of the pair of substrates toward the one of the pair of substrates, a backlight unit having a reflector and a light guide plate for reflecting the light which has entered the transmissive area from the side of the one of the pair of substrates and which has been transmitted by the area to cause the light to enter the transmissive area again from the side of the other of the pair of substrates, and a color filter layer formed only in the transmissive area of the pixel region.

This is a divisional of application Ser. No. 10/955,247, filed Sep. 30,2004 now U.S. Pat. No. 7,250,996.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display and a methodof manufacturing the same and, more particularly, to a transflectiveliquid crystal display capable of display in both of transmissive andreflective modes and a method of manufacturing the same.

2. Description of the Related Art

Recently, active matrix liquid crystal displays having a thin filmtransistor (TFT) at each of pixels are widely used as displays in everyfield of application. Under such a circumstance, transflective liquidcrystal displays capable of display in both of reflective andtransmissive modes have been put in use as displays for mobile terminalsor notebook type personal computers.

FIGS. 47A and 47B show a configuration of a transflective liquid crystaldisplay according to the related art disclosed in Non-Patent Document 1.FIG. 47A shows a configuration of a pixel of the transflective liquidcrystal display, and FIG. 47B shows a sectional configuration of thetransflective liquid crystal display taken along the line X-X in FIG.47A. As shown in FIGS. 47A and 47B, the pixel region is divided into atransmissive area T and a reflective area R. In the reflective area R ona TFT substrate 102, an insulator (resin layer) 130 is formed such thatthe reflective area R has a cell thickness that is one-half of a cellthickness of the transmissive area T. A reflective electrode 116 havingan irregular surface is formed on the insulator 130. In the middle ofthe transmissive area T on an opposite substrate 104, a protrusion 132for regulating the alignment of a vertical alignment type liquid crystal106 is formed. A pair of ¼ wave plates 120 are provided on respectivesides of the TFT substrate 102 and the opposite substrate 104 thatconstitute the exterior of the panel. A pair of polarizers 122 isprovided outside the ¼ wave plates 120, respectively. A step for formingand patterning the insulators 130 is required for this transflectiveliquid crystal display to make the cell thickness of the reflectiveareas R smaller than the cell thickness of the transmissive areas T.This results in a problem in that the manufacturing cost of the liquidcrystal display is increased because of increased complicatedness ofmanufacturing steps.

As a solution to this problem, a transflective liquid crystal displayhaving a configuration as shown in FIG. 48 was proposed in a JapanesePatent Application (numbered 2003-95329) made by the applicant. As shownin FIG. 48, a plurality of gate bus lines 150 extending in thehorizontal direction in the figure are formed substantially in parallelwith each other on a TFT substrate of a liquid crystal display. Aplurality of drain bus lines 152 extending in the vertical direction inthe figure are formed substantially in parallel with each other suchthat they intersect the gate bus lines 150, an insulation film, which isnot shown, being interposed between them. A TFT 154 is formed in thevicinity of each of intersections between the gate bus lines 150 and thedrain bus lines 152. Regions surrounded by the gate bus lines 150 andthe drain bus lines 152 constitute pixel regions. Storage capacitor buslines 156 substantially in parallel with the gate bus lines 150 areformed such that they extend across the pixel regions substantially inthe middle thereof. A storage capacitor electrode 158 is formed on thestorage capacitor bus line 156 at each pixel region.

A pixel electrode constituted by a transparent conductive film is formedat a pixel region. A pixel electrode has a rectangular circumference,and it has a plurality of electrode units 162 smaller than the pixelregion, electrode blank sections (slits) 164 formed between adjoiningelectrode units 162, and connecting electrodes 166 for electricallyconnecting electrode units 162 separated by the slits 164 with eachother. A plurality of spaces 168 are formed at the periphery of theelectrode units 162, the spaces being cutouts on respective side edgeswhich extend substantially in parallel with the gate bus lines 150 ordrain bus lines 152. A black matrix (BM) 170 for shielding a regionoutside the pixel region from light is formed on the opposite substrate.

In this configuration, the storage capacitor electrode 158 is used as areflector, and circular reflectors 172 are separately formed in thepixel region. The reflectors 172 are formed of the same material as thatof a gate electrode or source and drain electrodes of the TFT 154 andare provided such that they substantially overlap the centers of theelectrode units 162 when viewed in a direction perpendicular to asubstrate surface. The reflectors 172 are in an electrically floatingstate.

In this configuration, the cell thickness of a reflective area is thesame as the cell thickness of a transmissive area. Therefore, thebirefringence of the reflective area is twice that of the transmissivearea because light passes through the same liquid crystal layer twice toenter and exit the cell. A problem therefore arises in that yellow isdisplayed in the reflective area while white is displayed in thetransmissive area when the same voltage is applied to the transmissivearea and the reflective area. A measure taken to suppress birefringenceis to decrease the tilt of liquid crystal molecules during display inthe reflective mode by decreasing the applied voltage.

Although the configuration shown in FIG. 48 allows manufacturing stepssimpler than those for the configuration shown in FIGS. 47A and 47B, itrequires an applied voltage to be adjusted for display in thetransmissive mode and for display in the reflective mode. Anotherproblem arises in that when intense external light enters during displayin the transmissive mode, the color of light reflected by a reflectivearea can be greatly different from the color of light transmitted by atransmissive area.

The followings are the description of related arts,

Patent Document 1: Japanese Patent Laid-Open No. JP-A-H11-183892

Patent Document 2: Japanese Patent Laid-Open No. JP-A-2002-341366

Patent Document 3: Japanese Patent Laid-Open No. JP-A-2001-166289

Patent Document 4: Japanese Patent No. 3380482

Patent Document 5: Japanese Patent Laid-Open No. JP-A-S57-155582

Patent Document 6: Japanese Patent Laid-Open No. JP-A-2001-242452

Patent Document 7: Japanese Patent Laid-Open No. JP-A-2002-350853

Patent Document 8: Japanese Patent Laid-Open No. JP-A-2000-47215

Patent Document 9: Japanese Patent Laid-Open No. JP-A-2000-111902

Patent Document 10: Japanese Patent Laid-Open No. JP-A-H11-242226

Patent Document 11: Japanese Patent Laid-Open No. JP-A-H11-281972

Non-Patent Document 1: Asia Display/IDW' 01, p. 133 (2001)

Non-Patent Document 2: SID 96 Digest, pp. 618-621

SUMMARY OF THE INVENTION

It is an object of the invention to provide a transflective liquidcrystal display which can achieve high display characteristics in bothof reflective and transmissive modes and a method of manufacturing thesame.

The above-described object is achieved by a liquid crystal displaycharacterized in that it has a pair of substrates provided opposite toeach other, a liquid crystal layer sealed between the pair ofsubstrates, a pixel region including a reflective area having areflector for reflecting light entering from the side of one of the pairof substrates and a transmissive area for transmitting light enteringfrom the other of the pair of substrates toward the one of the pair ofsubstrates, a reflective section for reflecting light which has enteredthe transmissive area from the side of the one of the pair of substratesand which has been transmitted by the transmissive area and for causingthe light to enter the transmissive area again from the side of theother of the pair of substrates, and a color filter layer formed only inthe transmissive area of the pixel region.

The invention makes it possible to provide a transflective liquidcrystal display which can achieve high display characteristics in bothof the reflective and transmissive modes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B show a configuration of a liquid crystal display in afirst mode for carrying out the invention;

FIGS. 2A and 2B are sectional views showing the configuration of theliquid crystal display in the first mode for carrying out the invention;

FIG. 3 shows a configuration of a liquid crystal display according toEmbodiment 1-1 in the first mode for carrying out the invention;

FIGS. 4A and 4B show sectional configurations of the liquid crystaldisplay according to Embodiment 1-1 in the first mode for carrying outthe invention;

FIG. 5 is a graph showing a process of calculating an optimum thicknessof a transparent resin layer;

FIG. 6 shows a sectional configuration of a liquid crystal displayaccording to Embodiment 1-2 in the first mode for carrying out theinvention;

FIG. 7 shows a sectional configuration of a modification of the liquidcrystal display according to Embodiment 1-2 in the first mode forcarrying out the invention;

FIG. 8 shows a configuration of a liquid crystal display according toEmbodiment 1-3 in the first mode for carrying out the invention;

FIGS. 9A and 9B show sectional configurations of the liquid crystaldisplay according to Embodiment 1-3 in the first mode for carrying outthe invention;

FIGS. 10A and 10B show a modification of the liquid crystal displayaccording to Embodiment 1-3 in the first mode for carrying out theinvention;

FIG. 11 shows a sectional configuration of a liquid crystal displayaccording to Embodiment 1-4 in the first mode for carrying out theinvention;

FIGS. 12A and 12B show a modification of the liquid crystal displayaccording to Embodiment 1-4 in the first mode for carrying out theinvention;

FIG. 13 shows a sectional configuration of a liquid crystal displayaccording to Embodiment 1-5 in the first mode for carrying out theinvention;

FIG. 14 shows a configuration of a liquid crystal display according toEmbodiment 1-6 in the first mode for carrying out the invention;

FIGS. 15A and 15B show a configuration of a liquid crystal display in asecond mode for carrying out the invention;

FIG. 16 is a sectional view showing the configuration of the liquidcrystal display in the second mode for carrying out the invention;

FIG. 17 is a sectional view showing a modification of the configurationof the liquid crystal display in the second mode for carrying out theinvention;

FIG. 18 shows a configuration of a liquid crystal display according toEmbodiment 2-1 in the second mode for carrying out the invention;

FIG. 19 shows a configuration of the liquid crystal display according toEmbodiment 2-1 in the second mode for carrying out the invention;

FIG. 20 shows a modification of the configuration of the liquid crystaldisplay according to Embodiment 2-1 in the second mode for carrying outthe invention;

FIG. 21 is a sectional view showing a configuration of a liquid crystaldisplay according to Embodiment 2-2 in the second mode for carrying outthe invention;

FIG. 22 is a sectional view showing a configuration of a liquid crystaldisplay according to Embodiment 2-3 in the second mode for carrying outthe invention;

FIG. 23 shows a configuration of the liquid crystal display according toEmbodiment 2-3 in the second mode for carrying out the invention;

FIG. 24 is a sectional view showing a configuration of a liquid crystaldisplay according to Embodiment 2-4 in the second mode for carrying outthe invention;

FIG. 25 shows a configuration of the liquid crystal display according toEmbodiment 2-4 in the second mode for carrying out the invention;

FIG. 26 shows a configuration of the liquid crystal display according toEmbodiment 2-4 in the second mode for carrying out the invention;

FIG. 27 shows a configuration of a liquid crystal display according toEmbodiment 2-5 in the second mode for carrying out the invention;

FIG. 28 is a sectional view showing the configuration of the liquidcrystal display according to Embodiment 2-5 in the second mode forcarrying out the invention;

FIG. 29 shows a configuration of a reflective liquid crystal displayaccording to the related art;

FIGS. 30A and 30B show a configuration of a transflective liquid crystaldisplay according to the related art;

FIG. 31 shows a configuration of a transflective liquid crystal displayaccording to the related art;

FIG. 32 shows a configuration of a liquid crystal display in a thirdmode for carrying out the invention;

FIGS. 33A and 33B are sectional views showing the configuration of theliquid crystal display in the third mode for carrying out the invention;

FIG. 34 shows a configuration of a liquid crystal display according toEmbodiment 3-2 in the third mode for carrying out the invention;

FIG. 35 is a sectional view showing the configuration of the liquidcrystal display according to Embodiment 3-2 in the third mode forcarrying out the invention;

FIG. 36 shows a configuration of a liquid crystal display according toEmbodiment 3-3 in the third mode for carrying out the invention;

FIG. 37 is a sectional view showing the configuration of the liquidcrystal display according to Embodiment 3-3 in the third mode forcarrying out the invention;

FIGS. 38A to 38D show examples of configurations of CF layers of aliquid crystal display in the third mode for carrying out the invention;

FIGS. 39A to 39C show examples of configurations of CF layers of aliquid crystal display in the third mode for carrying out the invention;

FIG. 40 is a sectional view showing a configuration of a transflectiveliquid crystal display according to the related art;

FIG. 41 is a sectional view showing a configuration of a transflectiveliquid crystal display according to the related art;

FIG. 42 shows a fundamental configuration of a liquid crystal display ina fourth mode for carrying out the invention;

FIG. 43 shows a fundamental configuration of a liquid crystal display inthe fourth mode for carrying out the invention;

FIG. 44 shows a configuration of a liquid crystal display according toEmbodiment 4-1 in the fourth mode for carrying out the invention;

FIG. 45 shows a configuration of a liquid crystal display according toEmbodiment 4-1 in the fourth mode for carrying out the invention;

FIGS. 46A to 46C show sectional configurations of reflective sheets;

FIGS. 47A and 47B show a configuration of a transflective liquid crystaldisplay according to the related art; and

FIG. 48 shows a configuration of a transflective liquid crystal display.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Mode for Carrying Out theInvention

A liquid crystal display and a method of manufacturing the same in afirst mode for carrying out the invention will now be described withreference to FIGS. 1A to 14. FIG. 1A shows a configuration of a pixel ofa TFT substrate of the liquid crystal display in the present mode forcarrying out the invention, and FIG. 1B shows a conceptual diagram ofthe pixel region. FIG. 2A shows a sectional configuration of the liquidcrystal display taken along the line A-A in FIG. 1A, and FIG. 2B shows asectional configuration of the liquid crystal display taken along theline B-B in FIG. 1A. As shown in FIGS. 1A to 2B, a liquid crystal 6which is, for example, a vertical alignment type is sealed between a TFTsubstrate 2 and an opposite substrate 4 provided opposite to each other.The TFT substrate 2 is formed on a glass substrate 10, and it has gatebus lines 12 and storage capacitor bus lines 18 extending in thehorizontal direction in FIG. 1A. For example, an insulation film 30constituted by a silicon nitride film (SiN film) is formed throughoutthe substrate over the gate bus lines 12 and the storage capacitor buslines 18. Drain bus lines 14 extending in the vertical direction in FIG.1A are formed on the insulation film 30, the drain bus lines 14 having amulti-layer structure constituted by an aluminum (Al) layer 50 having arelatively high optical reflectivity and a molybdenum (Mo) layer 52having a relatively low optical reflectivity. A protective film 32 isformed throughout the substrate over the drain bus lines 14.

TFTs 20 are formed in the vicinity of positions where the gate bus lines12 and the drain bus lines 14 intersect each other. Gate electrodes ofthe TFTs 20 are formed of the same material as that of the gate buslines 12. Source electrodes and drain electrodes of the TFTs are formedof the same material as that of the drain bus lines 14.

A pixel region is generally divided into three areas and, as shown inFIG. 1B, it has a reflective area R provided in a central section wherea storage capacitor electrode (intermediate electrode) is formed and twotransmissive areas T provided above and below the reflective area R inthe figure, respectively. A reflector 54 formed of the same material asthat of the drain bus lines 14 is formed on the protective film 32 inthe reflective area R. A pixel electrode 16 constituted by a transparentconductive film such as an ITO is formed on the protective film 32 inthe reflective area R and the transmissive areas T. A pixel electrode 16of the reflective area R and the transmissive areas T in one pixel areelectrically connected to each other. Exactly speaking, an area in whicha reflector 54 is formed constitutes a reflective area R.

The pixel electrode 16 is electrically connected to the reflector 54through an opening provided by removing the protective film 32 on thereflector 54 through etching. In addition, the Mo layer 52 of thereflector 54 is removed through etching along with the protective film32. Therefore, the reflector 54 has a reflective surface 55 that is apart of the Al layer 50 having the higher optical reflectivity thusexposed. The reflector 54 also serves as one of electrodes of a storagecapacitor.

The opposite substrate 4 has a transparent resin layer (transparentlayer) 56 that is formed at least in a part of a reflective area R. Acolor filter (CF) layer 40 for each pixel is formed on the transparentresin layer 56. In the region where the transparent resin layer 56 isformed, since the thickness of the CF layer 40 is smaller than that inother regions, the absorption of light by the CF layer 40 is suppressed,and the reflective area R has an optical transmittance higher than thatof the transmissive area T. A common electrode 42 constituted by atransparent conductive film such as an ITO is formed on the CF layers 40throughout a display area of the substrate. A transparent resin layer (atransparent dielectric layer) 58 is formed on the common electrode 42 inthe reflective area R to decrease an effective voltage applied to theliquid crystal 6 in the reflective area R. An alignment controllingprotrusion 44 for controlling alignment of the liquid crystal 6 isformed of a resin on the transparent resin layer 58.

A method of manufacturing the TFT substrate 2 constituting the liquidcrystal display in the present mode for carrying out the invention willnow be described. First, a metal layer is formed on an entire surface ofthe glass substrate 10 and patterned to form the gate bus lines 12 andthe storage capacitor bus lines 18. Next, a SiN film is formedthroughout the substrate over the gate bus lines 12 and the storagecapacitor bus lines 18 to provide the insulation film 30. An activesemiconductor layer and a channel protection film for the TFTs 20 areformed on the insulation film 30, and the Al layer 50 and the Mo layer52 are then formed in the order listed throughout the substrate andpatterned to form source electrodes and drain electrodes of the TFTs 20,the drain bus lines 14 and the reflectors 54. Next, a protective film 32is formed throughout the source electrodes, the drain electrodes, thedrain bus lines 14 and the reflectors 54. The protective film 32 on thesource electrodes of the TFTs 20 is then removed through etching to formcontact holes. In the present mode for carrying out the invention, theprotective film 32 on the reflectors 54 is removed through etching atthe same time when the contact holes are formed. This step utilizes anetchant which dissolves SiN and Mo but does not dissolve Al. Thus, theMo layers 52 are removed along with the protective film 32 on thereflectors 54 to expose the Al layers 50, and the reflective surfaces 50having a high reflectivity are thus formed. Thereafter, the pixelelectrodes 16 are formed in the transmissive areas T and the reflectiveareas R of the pixel regions. The pixel electrodes 16 are electricallyconnected to the source electrodes of the TFTs 20 through the contactholes.

In the present mode for carrying out the invention, reflectivity isimproved by suppressing absorption of light at the CF layers 40 of thereflective areas R.

In the present mode for carrying out the invention, a voltage which issubstantially applied to the liquid crystal 6 in a reflective area R isdecreased by the transparent resin layer 58 formed on the commonelectrode 42 in the reflective area R. Thus, the voltage applied to theliquid crystal 6 varies between the respective transmissive areas T andthe reflective area R. As a result, even when liquid crystal moleculesin the transmissive areas T are greatly tilted, liquid crystal moleculesin the reflective area R are not so much tilted. Thus, substantiallyequal optical effects are achieved in the transmissive areas T throughwhich light passes once and the reflective area R through which lightpasses twice, and transmittance and reflectivity undergo similar changesin response to the applied voltage. Therefore, display is substantiallyequally performed in transmissive areas T and the reflective area R.

Further, in the present mode for carrying out the invention, thealignment controlling protrusions (banks) 44 formed on the commonelectrode 42 have a function of bending the direction of an electricfield. Since liquid crystal molecules tend to become perpendicular tothe direction of an electric field, liquid crystal molecules are thusaligned such that they are inclined toward the alignment controllingprotrusions 44.

In the present mode for carrying out the invention, the reflectors 54are formed of the same material as that of the source and drainelectrodes of the TFTs 20 and the drain bus lines 14, and the reflectorshave the reflective surfaces 55 which are exposed parts of the layers 50of Al that is a metal having a high reflectivity. The reflectivesurfaces 55 are formed at the same time when the protective film 32 ispatterned to form the contact holes. Thus, the reflectors 54 having ahigh reflectivity can be obtained without an additional manufacturingstep. The reflectors 54 may be formed of the same material as that ofthe gate electrode of the TFTs 20 and the gate bus lines 12.

Furthermore, in the present mode for carrying out the invention, thepixel electrodes 16 made of an ITO are formed so as to cover thereflective surfaces 55, and the top surfaces of all the electrodesformed on the substrates 2 and 4, respectively, are constituted by anITO. The substrates are thus electrically symmetric and are thereforeless likely to cause image persistence.

Liquid crystal displays in the present mode for carrying out theinvention will now be specifically described with reference to preferredembodiments of the same.

Embodiment 1-1

A liquid crystal display according to Embodiment 1-1 in the present modefor carrying out the invention will now be described. FIG. 3 shows aconfiguration of a pixel of the liquid crystal display of the presentembodiment. A configuration of a TFT substrate 2 is shown on the leftside of FIG. 3, and FIG. 3 shows the TFT substrate 2 and an oppositesubstrate 4 in an overlapping relationship with each other on the rightside thereof. FIG. 4A shows a sectional configuration taken along theline C-C in FIG. 3, and FIG. 4B shows a sectional configuration takenalong the line D-D in FIG. 3. As shown in FIGS. 3, 4A and 4B, one pixelregion is divided into a reflective area R which is provided in themiddle thereof and two transmissive areas T which are provided above andunder the reflective area R respectively in FIG. 3.

In a transmissive area T, a pixel electrode 16 is formed in asubstantially rectangular shape (e.g., a square shape). At the peripheryof the pixel electrode 16, in order to stabilize alignment of a liquidcrystal 6, a plurality of spaces 60 are formed by cutting side edges ofthe electrode diagonally to a gate bus line 12 and a drain bus line 14,the spaces being-patterned in the form of microscopic spines. Alignmentcontrolling protrusions 44 are formed of a photo-resist on the oppositesubstrate 4 in the middle of the transparent areas T, the protrusions 44being rhombic in their plan configuration and having a height in therange from 1 to 2 μm.

In the reflective area R, a transparent resin layer 56 is formed of, forexample, PC403 or PC441 (manufactured by JSR Corp.) in a part of theopposite substrate 4. A CF layer 40 is formed so as to cover thetransparent resin layer 56. Reflectivity is improved in the region wherethe transparent resin layer 56 is formed because the CF layer 40 has asmaller thickness and therefore absorbs a smaller quantity of light. Atransparent resin layer 58 is further formed on the common electrode 42to decrease a voltage that is substantially applied to the liquidcrystal layer in the reflective area R. The transparent resin layer 58is also formed of PC403, for example. The thickness of the transparentresin layer 58 is set at an optimum thickness in the range from about 1to 1.5 μm which will be described later. An alignment controllingprotrusion 44 is formed of a photo-resist on the transparent resin layer58 in the middle of the reflective area R, the protrusion being rhombicin its plan configuration and having a height in the range from 1 to 2μm similarly to those in the transmissive areas T.

FIG. 5 is a graph showing luminance/voltage characteristics relative tothe thickness of the transparent resin layer 58. The abscissa axis ofFIG. 5 represents voltages (V) applied between the electrodes 16 and 42,and the ordinate axis represents relative magnitudes of luminance oftransmitted light and reflected light. As shown in FIG. 5, when thetransparent resin layer 58 is not formed, luminance is reduced at avoltage which provides high luminance in the transmissive areas T. Onthe contrary, it will be understood that characteristics similar tothose of transmissive display can be achieved when the transparent resinlayer 58 is formed with a thickness in the range from 1.0 to 2.0 μm. Inparticular, when the transparent resin layer 58 has a thickness of 1.5μm, luminance is maximized and characteristics closer to those oftransmissive display can be achieved at an applied voltage of about 5 V.

The reflector 54 in the reflective area R is formed by stacking an Allayer 50 formed of the same material as that of source and drainelectrodes of the TFT 20 and the drain bus lines 14 and a Mo layer 52 asan upper layer. The reflector 54 has a reflective surface 55 which isthe AL layer 50 exposed by removing the upper Mo layer 52. After aprotective film (SiN film) 32 is formed, the reflective surface 55 isformed by removing the Mo layer 52 at the same time when a step isperformed to form a contact hole 34 for connecting the source electrodeof the TFT 20 and the pixel electrode 16 by removing the protective film32. This step utilizes an etchant which dissolves SiN and Mo, but doesnot dissolve Al. The pixel electrode 16 is simultaneously formed in thereflective area R and the transmissive area T after the reflectivesurface 55 is formed. The pixel electrode 16 is formed such that itcovers the reflective surface 55 to prevent the Al layer 50 fromcontacting the liquid crystal 6.

Embodiment 1-2

A liquid crystal display according to Embodiment 1-2 in the present modefor carrying out the invention will now be described. FIG. 6 shows asectional configuration of a pixel of the liquid crystal display of thepresent embodiment. While a CF layer 40 is formed on a transparent resinlayer 56 in the above described Embodiment 1-1, a transparent resinlayer 56 and a CF layer 40 are formed in reverse order in the presentembodiment as shown in FIG. 6. Specifically, after removing a part of aCF layer 40 (e.g., a central part of a reflective area R) entirely inthe thickness direction of the layer, a transparent resin layer 56 isformed on the same. Thus, a transparent area having no CF layer 40 isformed in a part of a reflective area R to improve the reflectivity ofthe same. Further, a common electrode 42, a transparent resin layer 58for decreasing an effective voltage applied to a liquid crystal 6 and analignment controlling protrusion 44 are sequentially formed on thetransparent resin layer 56. In the present embodiment, leveling isfacilitated because the transparent resin layer 56 is formed on the CFlayer 40.

FIG. 7 shows a modification of the configuration of the liquid crystaldisplay of the present embodiment. In the present modification, a commonelectrode 42 is formed after removing a part of the CF layer 40. Atransparent resin layer 57 is then formed in the region on the commonelectrode 42 where the CF layer 40 has been removed to form an alignmentcontrolling protrusion 44. The transparent resin layer 57 has both ofthe function of the transparent resin layer 56 of improving reflectivityin the reflective area R and the function of the transparent resin layer58 of decreasing the effective voltage applied to the liquid crystal 6.As a result, a liquid crystal display having the same functions as thoseof the configuration shown in FIG. 6 can be manufactured with simplifiedprocesses.

Embodiment 1-3

A liquid crystal display according to Embodiment 1-3 in the present modefor carrying out the invention will now be described. FIG. 8 shows aconfiguration of a pixel of the liquid crystal display of the presentembodiment. FIG. 9A shows a sectional configuration of the liquidcrystal display taken along the line E-E in FIG. 8, and FIG. 9B shows asectional configuration of the liquid crystal display taken along theline F-F in FIG. 8. In the present embodiment, the configuration shownin FIG. 7 is elaborated, and a measure is taken to improve a regionwhere a CF layer 40 is removed. First, a CF layer 40, from which anentire area where a reflector 54 is to be formed (a reflective area R)have been removed, is formed on a TFT substrate 2. A common electrode 42is thereafter formed on the CF layer 40. Then, a transparent resin layer57 is formed so as to fill the area where the CF layer 40 has beenremoved, and an alignment controlling protrusion 44 is formed on thetransparent resin layer 57. Alternatively, an entire area where areflective surface 55 is to be formed (which is smaller than thereflective area R as a whole) may be removed from the CF layer 40.

In the configuration of the present embodiment, since the CF layer 40 isnot formed in the reflective area R, light reflected by a reflector 54will have substantially no color. Therefore, transmissive areas Tareutilized for color display in the reflective mode. External light whichhas entered the transmissive areas T is partially reflected from theside of a backlight. The light is colored because it passes through theCF layer 40. Color display can be achieved with high luminance in thereflective mode by using the colored reflected light which passesthrough the transmissive areas T and the reflected light having no colorwhich passes through the reflective area R.

FIG. 10A shows a modification of the configuration of the presentembodiment. As shown in FIG. 10A, a CF substrate 4 of this modificationis provided with a CF layer 40′ as a transparent dielectric layerinstead of the transparent resin layer 57 shown in FIG. 9A. The hue ofthe CF layer 40′ is the same as the hue of a CF layer 40 in the samepixel. Specifically, when the CF layer 40 was in red, the CF layer 40′was also in red; when the CF layer 40 was in green, the CF layer 40′ wasalso in green; and when the CF layer 40 was in blue, the CF layer 40′was also in blue. Since the CF layer 40′ is provided in a reflectivearea R, light passes through the same twice, i.e., when it enters thelayer and when it exits the same. Therefore, the CF layer 40′ employedhad low color purity and a light tint. The transmissive areas T and thereflective area R were made to have the same tint consequently in adisplay state.

FIG. 10B shows another modification of the configuration of the presentembodiment. As shown in FIG. 10B, a transparent resin layer 57 similarto the transparent resin layer shown in FIG. 9A is used in thismodification, and an improvement is made on the CF layer 40. The CFlayer 40 is removed halfway in the thickness direction of the layer suchthat the thickness of the CF layer 40 becomes small in a portion thereofassociated with the transparent resin layer 57 to allow tint adjustment.Further, the thickness of the transparent resin layer 57 is adjusted tomake the thickness of the liquid crystal layer substantially uniform.Since the reflective area R was formed with a region 59 where thethickness of the CF layer 40 was small, it was possible to color thereflective area R too. Referring to a method of providing theconfiguration shown in FIG. 10B, the CF layer 40 was formed using anegative resist, and the portion of the same associated with the region59 was irradiated with light that was less intense than in otherportions using the half exposure technique.

Embodiment 1-4

A liquid crystal display according to Embodiment 1-4 in the present modefor carrying out the invention will now be described. FIG. 11 shows asectional configuration of the liquid crystal display of the presentembodiment. As shown in FIG. 11, a transparent resin layer 57 isprovided with light scattering properties in the present embodiment. Thetransparent resin layer 57 having light scattering properties scatterslight which has entered the same in an oblique direction, and the lightreaches a reflector 54 to be reflected by the same, the light beingscattered again when it exits. Thus, the light which has entered in anoblique direction exits the display screen in a direction square to thesame. As a result, reflective display could be performed with highluminance. Alternatively, a polarizer 70 which is applied to a viewer'sside of an opposite substrate 4 may be provided with light scatteringproperties. Further, diffusing paste having light scattering propertiesmay alternatively be applied to the polarizer 70.

FIGS. 12A and 12B show modifications of the present embodiment. Themodifications have a configuration in which a CF layer 40 remains in areflective area R and in which a cell thickness of a liquid crystallayer 6 becomes small in the reflective area R.

In the example shown in FIG. 12A, a transparent resin layer 56 was firstformed in a part of or throughout a reflective area R, and a CF layer 40was formed on the same. The thickness of the CF layer 40 on thetransparent resin layer 56 is equal to or smaller than the thickness ofthe CF layer 40 in other areas. A common electrode 42 constituted by anITO was formed on the top surface of the area. As a result, aconfiguration is provided in which the cell thickness in the reflectivearea R is equal to or smaller than the cell thickness in transmissivearea T and in which the transmittance of the CF layer 40 in thereflective area R is higher than the transmittance of the CF layer 40 inthe transmissive area T.

In the example shown in FIG. 12B, a CF layer 40 was first formed, andthe layer was then patterned to remove its part located in a reflectivearea R partially or entirely. Thereafter, a transparent resin layer 56was formed in a part of or throughout the reflective area R. That is,the transparent resin layer 56 is formed on the CF layer 40 and in apart of the CF layer 40 (and on the same part). The thickness of thetransparent resin layer 56 was adjusted such that the cell thickness inthe area where the transparent resin layer 56 was formed would be equalto or smaller than the cell thickness in a transmissive area T. As aresult, a configuration is provided in which the cell thickness in thereflective area R is equal to or smaller than the cell thickness intransmissive area T and in which the transmittance of the CF layer 40 inthe reflective area R is higher than the transmittance of the CF layer40 in the transmissive area T.

Embodiment 1-5

A liquid crystal display according to Embodiment 1-5 in the present modefor carrying out the invention will now be described. FIG. 13 shows asectional configuration of the liquid crystal display of the presentembodiment. As shown in FIG. 13, in the present embodiment, a columnarspacer 72 is formed by stacking CF layers 40G, 40R and 40B in threecolors, a common electrode 42, a resin layer 57′ formed of the samematerial as that of a transparent resin layer 57 and a resin layer 44′formed of the same material as that of an alignment controllingprotrusion 44 in the order listed. Since the resin layers 57′ and 44′are formed on the common electrode 42, it is possible to preventshorting between the common electrode 42 and a pixel electrode 16provided on a TFT substrate 2.

Embodiment 1-6

A liquid crystal display according to Embodiment 1-6 in the present modefor carrying out the invention will now be described. FIG. 14schematically shows a configuration of the liquid crystal display of thepresent embodiment. As shown in FIG. 14, a prism sheet 82, a diffusingsheet 84 and a backlight unit 88 are provided behind a liquid crystaldisplay panel 80, the elements being listed in the order of theircloseness to the panel. The backlight unit 88 has a fluorescent tube 92,a light guide plate 86 provided behind the diffusing sheet 84 forguiding light from the fluorescent tube 92 and a reflector (reflectivesection) 90 provided behind the light guide plate 86 and having a highoptical reflectivity. The reflector 90 reflects external light which haspassed through transmissive areas T of the liquid crystal display panel80 toward a viewer. Thus, even in a configuration in which no CF layer40 is formed in reflective areas R, color display can be performed inthe reflective mode by utilizing colored reflected light which haspassed through the transmissive areas T formed with CF layers 40. Inparticular, high reflection characteristics can be achieved by using aso-called reflector which has a silvered surface (silver reflector) asthe reflector 90.

As described above, the present mode for carrying out the inventionmakes it possible to provide a transflective liquid crystal displaywhich can achieve high luminance even in the reflective mode and whichcan achieve high display characteristics in both of the reflective andtransmissive modes.

Second Mode for Carrying Out the Invention

A liquid crystal display and a method of manufacturing the same in asecond mode for carrying out the invention will now be described withreference to FIGS. 15 to 28.

In the liquid crystal display in the first mode for carrying out theinvention shown in FIGS. 1A to 2B, the reflective surface 55 is flat.Therefore, reflected light has strong directivity which results indegradation of viewing angle characteristics of display in thereflective mode. Further, since reflectivity is low when external lightwhich has entered in a direction oblique to the display screen is viewedin a direction square to the display screen, a problem arises in thatpreferable display characteristics may not be obtained in the reflectivemode.

FIG. 15A shows a configuration of a pixel of a TFT substrate of a liquidcrystal display in the present mode for carrying out the invention inwhich the above-described problem is solved. FIG. 15B is a conceptualdiagram of the pixel region. FIG. 16 shows a sectional configuration ofthe liquid crystal display taken along the line G-G shown in FIG. 15A.As shown in FIGS. 15A, 15B and 16, a storage capacitor bus line 18formed of the same material as that of a gate electrode of a TFT 20 hasa plurality of protrusions 18 a extending substantially in parallelwith, for example, a drain bus line 14 in a lower part of a reflectivearea R as illustrated and patterned in a form of a comb. The storagecapacitor bus line 18 also has a plurality of openings extendingsubstantially in parallel with, for example, a gate bus line 12 in alower part of a reflective area R as illustrated. The storage capacitorbus line 18 in the reflective area R serves as a pattern for formingirregularities.

An insulation film 30 is formed throughout the substrate over thestorage capacitor bus line 18, and a reflector 54 is formed on theinsulation film 30 in the reflective area R. Irregularities that followthe shape of the irregularity forming pattern are formed on a reflectivesurface 55 of the reflector 54, and at least a part of the reflectivesurface 55 is inclined relative to the surface of the substrate. Whilethe irregularity forming pattern is formed of the same material as thatof the gate electrode of the TFT 20 in the present example, an a-Silayer or a SiN layer of which the TFT 20 is formed may alternatively beused as the pattern.

FIG. 17 shows a modification of the configuration of the liquid crystaldisplay in the present mode for carrying out the invention. As shown inFIG. 17, the present modification employs a combination of a TFTsubstrate 2 having a configuration similar to that shown in FIG. 16 anda CF substrate 4 that is a modification of the configuration shown inFIG. 12B. A CF layer 40 on the CF substrate 4 is patterned such that itis removed in a part of the reflective area R. The size of the blanksection of the CF layer 40 is set equal to or smaller than the size ofthe reflective area R. A transparent resin layer 56 is provided on theCF layer 40 and the blank section in the reflective area R. Thethickness of the transparent resin layer 56 is adjusted such that thecell thickness in the reflective area R becomes one-half of the cellthickness in a transmissive area T. A common electrode 42 constituted byan ITO is formed on top surfaces of the transparent resin layer 56 andthe CF layer 40. Further, an alignment controlling protrusion (bank) 45is formed on the common electrode 42. The alignment controllingprotrusion 45 is formed with a height of about 2 μm such that it alsoserves as a spacer. On the TFT substrate 2, a storage capacitor bus line18 is patterned to form an irregularity forming pattern such asprotrusions 18 a or openings 18 b (not shown in FIG. 17). As a result,irregularities that follow the shape of the irregularity forming patternare formed on a reflective surface 55 of a reflector 54. Thisconfiguration makes it possible to provide a transflective liquidcrystal display having the highest level of display quality withoutmaking any change in ordinary steps for manufacturing a transflectiveliquid crystal display.

In the present mode for carrying out the invention, at least a part ofthe reflective surface 55 of the reflector 54 can be formed at aninclination to the surface of the substrate. Therefore, external lightwhich has entered in a direction oblique to the display screen can bereflected in a direction square to the display screen. This improvesreflectivity and viewing angle characteristics.

Liquid crystal displays and methods of manufacturing the same in thepresent mode for carrying out the invention will now be specificallydescribed with reference to embodiments thereof.

Embodiment 2-1

First, a liquid crystal display according to Embodiment 2-1 in thepresent mode for carrying out the invention will be described. FIG. 18shows a configuration of a pixel of the liquid crystal display of thepresent embodiment. As shown in FIG. 18, in a reflective area R in themiddle of the pixel region, two irregularity forming patterns 62 areformed on both sides of a storage capacitor bus line 18 at the same timewhen a gate electrode of a TFT 20 and the storage capacitor bus line 18are formed, the patterns being formed of the same material as that ofthe gate electrode and the storage capacitor bus line 18. Theirregularity forming patterns 62 and the storage capacitor bus line 18are provided with a predetermined gap (indicated by a symbol *) leftbetween them to electrically isolate them from each other. That is, theirregularity forming patterns 62 are in an electrically floating state.The irregularity forming patterns 62 are formed with a substantiallyrectangular outline, and they have a plurality of circular openings 64.

FIG. 19 shows a modification of the configuration of the liquid crystaldisplay of the present embodiment. As shown in FIG. 19, a plurality ofcircular patterns 62 for forming irregularities are formed of the samematerial as that of the gate electrode of the TFT 20 in the reflectivearea R in the middle of the pixel region. The plurality of irregularityforming patterns 62 are electrically isolated from the storage capacitorbus line 18 and are in an electrically floating state.

FIG. 20 shows a configuration of a major part of another modification ofthe liquid crystal display of the present embodiment. In the presentmodification, a plurality of independent irregularity forming patterns62 d having a configuration similar to that in FIG. 19 are formed. Aplurality of openings 62 e having a configuration similar to that inFIG. 18 are formed in a part of the storage capacitor bus line 18. Thearea of the storage capacitor bus line 18 which is patterned to form theopenings 62 e also serves as an irregularity forming pattern. In orderto keep the resistance of the storage capacitor bus line 18 constant, awidth 18 d of the area of the storage capacitor bus line 18 which ispatterned to form the openings 62 e is greater than a width 18 c of thestorage capacitor bus line 18 in other areas thereof. Further, in orderto prevent interference, each of the irregularity forming patterns 62 dand the openings 62 e is irregularly arranged. Since irregularities canbe thus formed on the surface of the reflector 54 even in its area abovethe storage capacitor bus line 18, display can be performed with higherluminance in the reflective mode.

Embodiment 2-2

A liquid crystal display and a method of manufacturing the sameaccording to Embodiment 2-2 in the present mode for carrying out theinvention will now be described. FIG. 21 shows a sectional configurationof a reflective area R of the liquid crystal display of the presentembodiment. As shown in FIG. 21, the liquid crystal display of thepresent embodiment has an irregularity forming pattern 62 in aconfiguration similar to that shown in FIGS. 15A, 15B and 16. Theirregularity forming pattern 62 has a metal layer (conductor layer) 62 awhich is formed of the same material as that of a gate electrode of aTFT 20 and a storage capacitor bus line 18, an a-Si layer (semiconductorlayer) 62 b which is provided on the metal layer 62 a with an insulationfilm 30 interposed between them and which is formed of the same materialas that of an active semiconductor layer of the TFT 20 and a SiN film(dielectric layer) 62 c which is formed on the a-Si layer 62 b using thesame material as that of a channel protection film of the TFT 20.Alternatively, the irregularity forming pattern 62 may be constituted bya metal layer 62 a and a SiN film 62 c. All of the metal layer 62 a, thea-Si layer 62 b and the SiN film 62 c have substantially the same planconfiguration.

Referring to steps for forming the irregularity forming pattern 62 ofthe present embodiment, a metal layer is first formed on an entiresurface of a glass substrate 10 and patterned to form a metal layer 62 asimultaneously with a gate electrode and a storage capacitor bus line18. Next, an insulation film 30 is formed throughout the substrate overthe metal layer 62 a. Then, an a-Si layer and a SiN film are formed inthe order listed on the entire top surface of the insulation film 30. Aresist is then applied to the entire top surface of the SiN film, andback exposure is performed using the metal layer 62 a as a mask.Development is thereafter performed to form a resist pattern which hasthe same shape as that of the metal layer 62 a. Next, only the SiN filmor both of the SiN film and the a-Si layer are etched using the resistpattern as a mask to form a SiN film 62 c (probably along with an a-Silayer 62 b) which has the same shape as that of the metal layer 62 a. Asthus described, in the present embodiment, the SiN film 62 c (probablyalong with the a-Si layer 62 b) is formed by performing back exposure.In the present embodiment, since the irregularity forming pattern 62 canbe provided with a greater substantial thickness, greater irregularitiescan be provided on a reflector 55.

Embodiment 2-3

A liquid crystal display and a method of manufacturing the sameaccording to Embodiment 2-3 in the present mode for carrying out theinvention will now be described. FIG. 22 shows a sectional configurationof a reflective area R of the liquid crystal display of the presentembodiment. As shown in FIG. 22, in the liquid crystal display of thepresent embodiment, a metal layer 62 a, an a-Si layer 62 b and a SiNfilm 62 c which constitute an irregularity forming pattern 62 aredifferent from each other in plan configuration. Alternatively, theirregularity forming pattern 62 may be constituted by a metal layer 62 aand a SiN film 62 c.

Referring to steps for forming the irregularity forming pattern 62 ofthe present embodiment, a metal layer is first formed on an entiresurface of a glass substrate 10 and patterned to form a metal layer 62 asimultaneously with a gate electrode and a storage capacitor bus line18. Next, an insulation film 30 is formed throughout the substrate overthe metal layer 62 a. Then, an a-Si layer and a SiN film are formed inthe order listed on the entire top surface of the insulation film 30. Aresist is then applied to the entire top surface of the SiN film, andexposure is performed from above the substrate using a predeterminedphoto-mask. Development is thereafter performed to form a resist patternhaving a predetermined shape.

Next, only the SiN film or both of the SiN film and the a-Si layer areetched using the resist pattern as a mask to form a SiN film 62 c (alongwith an a-Si layer 62 b) which has the predetermined shape. As thusdescribed, in the present embodiment, the SiN film 62 c (along with thea-Si layer 62 b) is formed by performing exposure from above thesubstrate instead of back exposure.

FIG. 23 shows an example of a configuration of an irregularity formingpattern 62 of a liquid crystal display according to the presentembodiment. As shown in FIG. 23, a plurality of concentric metal layers62 a is formed in a reflective area R in the middle of a pixel. Aplurality of SiN films 62 c and a-Si layers 62 b extending substantiallyin parallel with a gate bus line 12 is formed in a part of thereflective area R that is located above a storage capacitor bus line 18in the figure, and a plurality of SiN films 62 c and a-Si layers 62 bextending substantially in parallel with a drain bus line 14 is formedin a part of the reflective area R that is located under the storagecapacitor bus line 18 in the figure. Thus, the irregularity formingpattern 62 is constituted by the metal layers 62 a, the a-Si layers 62 band the SiN films 62 c which are different from each other in planconfiguration.

Embodiment 2-4

A liquid crystal display and a method of manufacturing the sameaccording to Embodiment 2-4 in the present mode for carrying out theinvention will now be described. FIG. 24 shows a sectional configurationof a reflective area R of the liquid crystal display of the presentembodiment. As shown in FIG. 24, in the liquid crystal display of thepresent embodiment, an irregularity forming pattern 62 has a metal layer62 a and an a-Si layer 62 b and a SiN film 62 c which are formed only onthe metal layer 62 a and which are patterned to be smaller than themetal layer 62 a. Alternatively, the irregularity forming pattern 62 maybe constituted by a metal layer 62 a and a SiN film 62 c.

Referring to steps for forming the irregularity forming pattern 62 ofthe present embodiment, a metal layer is first formed on an entiresurface of a glass substrate 10 and patterned to form a metal layer 62 asimultaneously with a gate electrode and a storage capacitor bus line18. Next, an insulation film 30 is formed throughout the substrate overthe metal layer 62 a. Then, an a-Si layer and a SiN film are formed inthe order listed on the entire top surface of the insulation film 30. Aresist is then applied to the entire top surface of the SiN film, andback exposure is performed using the metal layer 62 a as a mask.Subsequently, exposure and development is performed from above thesubstrate using a predetermined photo-mask to form a resist patternwhich is provided only on the metal layer 62 a and which is patterned tobe smaller than the metal layer 62 a. Next, only the SiN film or both ofthe SiN film and the a-Si layer are etched using the resist pattern as amask to form a SiN film 62 c (along with an a-Si layer 62 b) which isprovided only on the metal layer 62 a and which is patterned to besmaller than the metal layer 62 a. As thus described, in the presentembodiment, the SiN film 62 c (along with the a-Si layer 62 b) is formedby performing back exposure and exposure from above the substrate.

FIGS. 25 and 26 show examples of configurations of an irregularityforming pattern 62 of a liquid crystal display according to the presentembodiment. As shown in FIG. 25, two metal layers 62 a are formed in areflective area R in the middle of a pixel, the metal layers beingprovided on both sides of a storage capacitor bus line 18. Each of thetwo metal layers 62 a has a substantially rectangular outline. Aplurality of circular openings 64 is formed in the metal layer 62 a thatis located above the storage capacitor bus line 18 in the figure.Further, there is formed a plurality of SiN films 62 c and a-Si layers62 b which are provided only above the metal layers 62 a in anoverlapping relationship with the metal layers 62 a and which arepatterned to be smaller than the metal layers 62 a. The plurality of SiNfilms 62 c and a-Si layers 62 b is substantially concentrically formed.Thus, an irregularity forming pattern 62 is constituted by the metallayers 62 a, the a-Si layers 62 b and the SiN films 62 c.

Embodiment 2-5

A liquid crystal display according to Embodiment 2-5 in the present modefor carrying out the invention will now be described. FIG. 27 shows aconfiguration of a pixel electrode of one pixel of the liquid crystaldisplay of the present embodiment. FIG. 28 shows a sectionalconfiguration of the liquid crystal-display taken along the line H-H inFIG. 27. As shown in FIGS. 27 and 28, for example, a transparent resinlayer 26 made of PC403 is formed on a TFT 20. Irregularities are formedin a part (in the vicinity of an area to serve as a reflective area R)of the surface of the transparent resin layer 26. The irregularities areformed using either method in which the transparent resin layer isirradiated with ultraviolet rays to modify the surface of the same andin which annealing is thereafter performed to form wrinkles on thesurface or method in which patterned exposure (including half exposure)is performed using a predetermined photo-mask to form an irregularpattern on the transparent resin layer 26. A contact hole 34 forexposing a source electrode 22 of the TFT 20 is formed in thetransparent resin layer 26. A pixel electrode 16 constituted by an ITOis formed in a predetermined shape on the transparent resin layer 26.Irregularities that follow the irregularities on the surface of thetransparent resin layer 26 are formed in the vicinity of an area, whichis to serve as a reflective area R, on the surface of the pixelelectrode 16. A reflective electrode 24 made of Al is formed in thereflective area R on the pixel electrode 16. As shown in FIG. 27, thereflective electrode 24 is provided in the middle of a pattern of thepixel electrode 16 that is substantially square. Irregularities thatfollow the irregularities on the surface of the pixel electrode 16 areformed on the surface of the reflective electrode 24, and at least apart of the surface (reflective surface) is inclined relative to thesurface of the substrate.

On a glass substrate 11 of an opposite substrate 4 provided opposite tothe above-described elements, a CF layer 40 is formed in areas otherthan the reflective area R where the reflective electrode 24 is formed.A common electrode 42 is formed throughout the substrate over the CFlayer 40. A transparent resin layer 57 is formed on the common electrode42 in the reflective area R.

In the present embodiment, at least a part of the surface of thereflective electrode 24 can be formed such that it is at an inclinationto the surface of the substrate. Therefore, external light which hasentered in a direction oblique to the display screen can be reflected ina direction square to the display screen. This improves reflectivity andviewing angle characteristics.

As described above, the present mode for carrying out the inventionmakes it possible to provide a liquid crystal display which can achievehigh luminance even in the reflective mode and which can achieve highdisplay characteristics in both of the reflective and transmissivemodes.

Third Mode for Carrying Out the Invention

A liquid crystal display in a third mode for carrying out the inventionwill now be described with reference to FIGS. 29 to 39C.

FIG. 29 shows the configuration of a reflective liquid crystal displayaccording to the related art disclosed in Non-Patent Document 2. Asshown in FIG. 29, a liquid crystal 106 is sealed between a pair ofsubstrates 102 and 104 provided opposite to each other. The state ofalignment of the liquid crystal 106 is a bend alignment that is alsoreferred to as “ROCB”. Reflective electrodes 116 having a flatreflective surface in the form of a mirror surface are formed on asurface of the substrate 102 facing the liquid crystal 106. A commonelectrode 142 constituted by a transparent conductive film is formed ona surface of the other substrate 104 facing the liquid crystal 106. Aphase difference film (¼ wave plate) 120, a polarizer 122, and anoptical path control film 124 are provided in the order list on the side(viewer's side) of the substrate 104 which constitutes the exterior ofthe panel.

The optical path of incident external light is bent by the optical pathcontrol film 124. The light then reaches the reflective electrodes 116and is reflected by the same to exit the panel toward a viewer. Sincethere is the optical path control film 124 which transmits light whilediffusing the same, beams of light reflected at the surface of theoptical path control film 124 have optical paths that are different fromthe optical paths of beams of light which pass through the opticalcontrol film 124 and which are reflected at the surface of thereflective electrodes 116. Therefore, display on the display screen willnot overlap external light when the viewer watches the screen, whichallows a displayed image to be clearly viewed.

However, the configuration of the reflective liquid crystal displayshown in FIG. 29 has not been successfully combined with a transmissivetype. The reason is that the liquid crystal 106 is aligned in hybridalignment on an assumption that light will pass through the liquidcrystal 106 twice in the reflective type. Hybrid alignment has a problemin that it disallows white to be sufficiently displayed becausebirefringence is too small to use in a transmissive type. There isanother problem in that viewing angle characteristics provided by thealignment are low for a transmissive type.

The transflective liquid crystal display shown in FIGS. 47A and 47B issimilar to the reflective liquid crystal display shown in FIG. 29 inthat the reflective electrodes 116 are formed inside the liquid crystaldisplay panel, but it is different in that irregularities are formed onthe reflective surfaces of the reflective electrodes 116. FIGS. 30A and30B are sectional views showing operations of the transflective liquidcrystal display shown in FIGS. 47A and 47B. FIG. 30A shows a state inwhich no voltage is applied to the liquid crystal 106, and FIG. 30Bshows a state in which a predetermined voltage is applied to the liquidcrystal 106. As shown in FIG. 30A, the liquid crystal 106 exerts nooptical effect on light when no voltage is applied because liquidcrystal molecules are aligned perpendicularly to a substrate surface.

When reflective display is performed, light which has passed through thepolarizer 122 enters the liquid crystal 106 after passing through the ¼wave plate 120, and the light passes through the ¼ wave plate 120 againafter being reflected by reflective electrode 116. That is, thepolarization of the light rotates at 90° because the light passesthrough the ¼ wave plate 120 twice. Therefore, the light is absorbed bythe polarizer 122. Black is thus displayed in the reflective mode.

When transmissive display is performed, light which has passed throughthe polarizer 122 on the side of the backlight unit 188 enters theliquid crystal 106 after passing through the ¼ wave plate 120, and thelight passes through the ¼ wave plate 120 on the viewer's side. That is,the polarization of the light rotates at 90° because the light passesthrough the ¼ wave plate 120 twice. Therefore, the light is absorbed bythe polarizer 122 on the viewer's side. Black is thus displayed in thetransmissive mode.

In the state in which a predetermined voltage is applied, since liquidcrystal molecules are tilted relative to the substrate surface, theliquid crystal 106 exerts a predetermined optical effect on light. Asshown in FIG. 30B, the polarization of light which has passed throughthe polarizer 122 is changed by the liquid crystal 106. As a result,white is displayed in both of the reflective and transmissive modes.

In this configuration, there is a need for providing the irregularreflecting electrodes 116. The formation of the irregular reflectiveelectrodes 116 necessitates manufacturing processes such as formationand patterning of a resin layer and formation of the reflectiveelectrodes 116 in addition to ordinary processes for manufacturingtransmissive liquid crystal displays. This has resulted in a significantincrease in the manufacturing cost of liquid crystal displays.

FIG. 31 shows a configuration of a transflective liquid crystal displayaccording to the related art disclosed in Patent Document 4. As shown inFIG. 31, in the transflective liquid crystal display, a pixel region isdivided into reflective areas R and transmissive areas T. Reflectiveelectrodes 116 are formed in the reflective areas R, and transparentpixel electrodes 117 are formed in the transmissive areas T. A cellthickness in the reflective areas R is smaller than a cell thickness inthe transmissive areas T because of an insulation film 118 formed on aTFT substrate 102. In the transmissive areas T, light from a backlightunit 188 exits toward a viewer after passing through a liquid crystallayer 106 once. In the reflective areas R, light which has entered theliquid crystal panel from a top surface thereof is reflected by thereflective electrodes 116, and the light exits toward the viewer afterpassing through the liquid crystal layer 106 twice. Therefore, if thecell thickness in the reflective areas R is equal to the cell thicknessin the transmissive areas T, retardation in the reflective areas R willbe twice that in the transmissive areas T. As a result, when thereflective electrodes 116 and the pixel electrodes 117 are at the samevoltage, the reflective areas R and the transmissive areas T havegradations completely different from each other. For example, when whiteis displayed in the transmissive mode, display in the reflective modehas a tint of yellow. In order to prevent this, in the configurationshown in FIG. 31, the cell thickness in the reflective areas R is madesmaller than the cell thickness in the transmissive areas T to make thereflective areas R and the transmissive areas T as close as possible toeach other in retardation.

It is most effective to make the cell thickness in the reflective areasR smaller than the cell thickness in the transmissive areas T ineliminating the difference between gradations in the reflective areas Rand the transmissive areas T.

However, it is required to form a structure (insulation film 118) forreducing the cell thickness in the reflective areas R in order to makethe cell thickness in the reflective areas R smaller than that in thetransmissive areas T. The structure can reduce the stability of thealignment of the liquid crystal 106 in sections that constituteboundaries between the reflective areas R and the transmissive areas T.In particular, when the liquid crystal 106 is in vertical alignmentwhich eliminates a need for a rubbing step, the alignment of the liquidcrystal 106 is regulated by the structure. Proper alignment orientationis thus disabled, which can cause roughness in display and alignmentdefects.

Patent Document 9 discloses a transflective liquid crystal displaydifferent from that described above. The transflective liquid crystaldisplay is similar to the configuration shown in FIG. 31 in that onepixel is divided into reflective areas R and transmissive areas T, butit is different in the configuration of a CF layer in the reflectiveareas R. A reflective area R has a section having a CF layer and asection having no CF layer, which provides luminance higher than that ina case wherein a CF layer is formed throughout the reflective area R,although there is a reduction in chromaticity.

In this configuration, however, since the CF layer is removed in a partof the reflective area, a step is formed on the surface of the substrateon which the CF layer is formed. The step can cause a variation of thecell thickness or an irregularity in the alignment of the liquid crystalwhich deteriorates display characteristics.

The present mode for carrying out the invention solves theabove-described problems and employs a measure to improve the stabilityof the alignment of a liquid crystal in vertical alignment by reducing adifference between gradations in a reflective area R and a transmissivearea T and to improve the stability of the alignment of the liquidcrystal when it is vertically aligned by making a step formed betweenthe reflective area R and the transmissive area T small.

FIG. 32 shows a configuration of a pixel on a TFT substrate of theliquid crystal display in the present mode for carrying out theinvention. FIG. 33A shows a sectional configuration of the liquidcrystal display taken along the line I-I in FIG. 32, and FIG. 33B showsa sectional configuration of the liquid crystal display taken along theline J-J in FIG. 32. As shown in FIGS. 32, 33A and 33B, the liquidcrystal display in the present mode for carrying out the invention hasan opposite substrate 4 on which a common electrode 42 is formed, a TFTsubstrate 2 on which pixel electrodes 16 are formed, and a verticalalignment type liquid crystal 6 sealed between the substrates 2 and 4which are provided opposite to each other. A configuration of a pixel onthe TFT substrate 2 is as follows.

Gate bus lines 12, drain bus lines 14 and TFTs 20 are formed on the TFTsubstrate 2. A first insulating resin layer 36 such as a transparentresin layer or a color filter layer is formed on them. A reflector 53 isformed in a reflective area R on the insulating resin layer 36. Thereflective area R having the reflector 53 formed therein is provided atthe periphery of a pixel region including areas above a gate bus line12, a drain bus line 14 and a TFT 20. The reflector 53 is in anelectrically floating state, or it is at the same potential as thecommon electrode 42 or at a ground potential. A second insulating resinlayer 37 is formed on the entire top surface of the reflector 53. Apixel electrode 16 having a predetermined shape constituted by atransparent metal layer such as an ITO is formed in a transmissive areaT (and in a part of the reflective area R) on the insulating resin layer37. The transmissive area T is provided in a central section of thepixel inside the reflective area R. The pixel electrode 16 formed in thetransmissive area T is provided in a region corresponding to an openingof the reflector 53 and is located in a layer above the reflector 53with the insulating resin layer 37 interposed between them from theviewpoint of the layer structure.

The liquid crystal display panel is sandwiched by a pair of circularpolarizers each of which is constituted by a polarizer and a ¼ waveplate. The optical axes of the polarizers are orthogonal to each other.An optical path control film is applied to the polarizer located on aviewer's side. A backlight is provided on a back side of the liquidcrystal display panel.

Liquid crystal molecules are aligned perpendicularly to surfaces of thesubstrates when no voltage is applied. First, when external lightenters, the light is reflected by the reflector 53 in the reflectivearea R. Since the circular polarizers are provided, the reflected lightis absorbed by the polarizers. Black is thus displayed. Light which hasentered from the backlight passes through the transmissive area T inwhich the reflector 53 is not formed. Light which has passed through thecircular polarizer on the back side of the liquid crystal display panelis transmitted without undergoing any change in its state ofpolarization because the liquid crystal is vertically aligned. Thetransmitted light is absorbed by the circular polarizer on the viewer'sside. Black is thus displayed.

When a voltage is applied, since liquid crystal molecules are tilted,the liquid crystal layer exhibits birefringence which is an opticaleffect, thereby causing a change in the state of polarization of light.The state of polarization of incident external light thus changes, andreflected light passes through the circular polarizer on the viewer'sside. Gray or white is thus displayed. Similarly, light which hasentered from the backlight also undergoes a change in its state ofpolarization and passes through the circular polarizer on the viewer'sside. Gray or white is thus displayed.

States of alignment of the liquid crystal and gradations of display inthe reflective area R and the transmissive area T will now be described.Since the pixel electrode 16 is formed in the transmissive area T,liquid crystal molecules in the region a in FIG. 33A are driven based ona voltage applied between the pixel electrode 16 and the commonelectrode 42. Therefore, the transparent area T exhibitsvoltage/gradation characteristics similar to those of configurationsaccording to the related art. Consideration is needed for the reflectivearea R. Liquid crystal molecules in the region β in FIG. 33A are drivenonly by the pixel electrode 16 in the transmissive area T. The pixelelectrode 16 is formed only in a part of the peripheral section of thereflective area R. In the reflective area R, liquid crystal moleculesare therefore driven by an oblique electric field generated at theperipheral section of the pixel electrode 16. In the reflective area R,a gradation is thus represented only by the tilt of liquid crystalmolecules caused by the oblique electric field. As a result, aneffective voltage applied to the liquid crystal layer in the entirereflective area R is lower than that in the transmissive area T. It istherefore possible to reduce a difference in display of a gradationbetween the reflective area R where light passes through the liquidcrystal layer twice and the transmissive area T where light passesthrough only once.

When a CF layer is provided under the reflector 53 on the TFT substrate2, the CF layer exerts its effect only on the transmissive area T. Sucha configuration eliminates a need for a step for providing the openingon the CF layer 40 provided on the opposite substrate 4 in thereflective area R.

Further, when a CF layer optimized for display in the reflective mode isprovided above the reflector 53 or on the opposite substrate 4, since nostep will be formed in the pixel region as a result of the removal of apart of the CF layer 40, color filter conditions in each of thereflective area R and the transmissive area T can be optimized.

Light diffusing properties in the reflective area R can be improved byproviding a hole in the CF layer provided under the reflector 53.Further, a film for scattering light entering in a predetermineddirection (a light scattering layer) may be provided on the viewer'sside of the opposite substrate 4.

In the present mode for carrying out the invention, there is no need formaking a cell thickness in the reflective area R smaller than a cellthickness in the transmissive area T. The cell thickness in thereflective area R is substantially equal to or greater than the cellthickness in the transmissive area T.

Liquid crystal displays in the present mode for carrying out theinvention will now be specifically described with reference to preferredembodiments.

Embodiment 3-1

First, a liquid crystal display according to Embodiment 3-1 will bedescribed with reference to FIGS. 32, 33A and 33B. The pitch of pixelsof the liquid crystal display of the present embodiment is 300 μm in thelongitudinal direction (a direction in which drain bus lines 14 extend;this holds true in the following description) and 100 μm in thetransverse direction (a direction in which gate bus lines 12 extend;this holds true in the following description). The drain bus lines 14and the gate bus lines 12 both having a width of 7 μm are formed on theTFT substrate 2. The drain bus lines 14 and the gate bus lines 12intersect each other with an insulation film 30 interposed between them.The insulation film 30 is constituted by a thin film layer mainlycomposed of SiO₂. TFTs 20 are formed in the vicinity of positions wherethe drain bus lines 14 and the gate bus lines 12 intersect each other. Asource electrode 22 of a TFT 20 extends up to an opening section of therelevant pixel, the electrode being constituted by the same layer as thedrain bus lines 14. In the middle of the pixel, a storage capacitor isformed by a storage capacitor bus line 18 extending in parallel with thegate bus lines 12 and a storage capacitor electrode 19 which is formedat each pixel.

A first insulating resin layer 36 having a thickness of about 2 μm and arelative dielectric constant of about 3.5 is formed on the TFT substrate2 on which the TFTs 20, drain bus lines 14 and the gate bus lines 12have been formed as described above. The insulating resin layer 36 isformed of a resin having a high degree of transparency such as anacrylic resin. Contact holes 34 for exposing pad sections of the sourceelectrodes 22 are formed in the insulating resin layer 36. The size ofthe contact holes 34 is 10×10 μm².

Reflectors 53 are formed on the insulating resin layer 36. Thereflectors 53 are formed by sputtering an Al thin film on the entire topsurface of the insulating resin layer 36 and sputtering the Al thin filmusing photolithography such that the film is left in a region extendinginto each pixel a distance of 7 μm from an edge of each of the bus lines12 and 14. Connecting electrodes 53′ connected to the source electrodes22 through the contact holes 34 may be formed at the same time when thereflectors 53 are formed.

A second insulating resin layer 37 having a thickness of about 2.5 μmand a relative dielectric constant of about 3.5 is formed throughout thesubstrate over the reflectors 53. The insulating resin layer 37 isformed of a resin having a high degree of transparency such as anacrylic resin similarly to the insulating resin layer 36. Contact holes34 of 10×10 μm² similar to those in the insulating resin layer 36 areformed in the insulating resin layer 37 for exposing the pad sections ofthe source electrodes 22.

Pixel electrodes 16 are formed on the insulating resin layer 37. Thepixel electrodes 16 are provided by sputtering an ITO on the entire topsurface of the insulating resin layer 37 to form a transparentconductive film thereon and by patterning the transparent conductivefilm using photolithography. The pixel electrodes 16 are formed atopenings of the reflectors 53 and are patterned such that they arealigned with the positions of edges of the reflectors 53. The pixelelectrodes 16 and the reflectors 53 are electrically independent of eachother. The pixel electrodes 16 are electrically connected to the sourceelectrodes 22 through the contact holes 34.

The pixel electrode 16 in one pixel is configured by combining aplurality of electrode units 17 which are electrically connected to eachother. The pixel electrode 16 shown in FIG. 32 is constituted by sixelectrode units 17 which are arranged in the longitudinal direction of apixel region, for example. The size of each electrode unit 17 is 35×78μm², and slits between adjoining electrode units 17 have a width of 8μm. A reflector 53 may be formed on the slits in addition to theperipheral section of the pixel region.

An electrode unit 17 has a solid electrode 17 a provided in the middlethereof and comb-shaped electrodes 17 b extending from the periphery ofthe solid electrode 17 a toward the periphery of the electrode unit 17.The solid electrode 17 a is in the form of a rectangle of 25×60 μm². Thecomb-shaped electrodes 17 b include an electrode 17 c (hereinafterreferred to as “backbone electrode”) having a width of 5 μm and a lengthof 15 μm which extends from the center of each side of the circumferenceof the solid electrode 17 a toward the periphery of the electrode unit17, the electrode 17 c being substantially perpendicular to therespective side of the solid electrode. The region except the solidelectrode 17 a is thus divided into four alignment regions at thebackbone electrodes 17 c which constitute boundaries. Linear electrodes17 d starting at the periphery of the solid electrode 17 a andterminating at the periphery of the electrode unit 17 are formed in eachof the alignment regions, the electrodes extending in a differentdirection in each of the alignment regions. Specifically, the linearelectrodes 17 d in each alignment region are in parallel with eachother, and the linear electrodes 17 d diagonally extend in directionsfrom a central section of the electrode unit 17 toward the respectivevertices of the circumference of the electrode unit 17. The linearelectrodes 17 d have a width of 3 μm, and slits between adjoining linearelectrodes 17 d have a width of 3 μm. The ends of the comb-shapedelectrodes 17 b at the periphery of the electrode unit 17 are formed asif they were cut in compliance with the sides of the circumference ofthe electrode unit 17. The comb-shaped electrodes 17 b partially overlapthe reflector 53 when viewed perpendicularly to the substrate surface,and some of the ends of the comb-shaped electrodes 17 b are locatedoutside the edge of the opening of the reflector 53.

The electrode units 17 in one pixel must be electrically connected toeach other. Connecting electrodes 15 for this purpose are formed byextending each backbone electrode 17 c facing another electrode unit 17across a slit among the backbone electrodes 17 c extending from thesolid electrode 17 a. That is, the connecting electrodes 15 areconnected to central sections of the sides of the circumference of theelectrode units 17 which are located adjacent to other electrode units17 with slits interposed therebetween. In the present embodiment, sincethere is only one electrode unit 17 in the transverse direction of thepixel region, the connecting electrodes 15 are provided only in thelongitudinal direction.

No black matrix is provided on the opposite substrate 4. The reflectors53 provided on the TFT substrate 2 are used as a substitute for a blackmatrix in transmissive areas T. CF layers 40 in red, green and blue(which are not shown in FIGS. 33A and 33B) are formed on the oppositesubstrate 4. A CF layer 40 is provided only in a transmissive area T.i.e., the opening of a reflective area R and is not provided in areflective area R. A transparent resin layer 57 (not shown) having athickness substantially equal to or smaller than the thickness of the CFlayer 40 is formed in a reflective area R. A common electrode 42constituted by an ITO is formed on the entire surfaces of the CF layer40 and the transparent resin layer 57. Alignment controlling protrusions44 having a diameter of 10 μm and a thickness of 2 μm made of an acrylicresin are formed in regions on the common electrode 42 corresponding tocentral sections of the electrode units 17 on the TFT substrate 2. Theprovision of the alignment controlling protrusions 44 makes singularpoints S=+1 formed at the central sections of the electrode units 17 onthe TFT substrate 2 stronger.

Alignment films are formed on the top surfaces of the substrates 2 and4. The alignment films have vertically aligning properties and alignliquid crystal molecules in a direction vertical to the substratesurfaces (alignment film surfaces) in a normal state. The liquid crystaldisplay in the present mode for carrying out the invention is fabricatedby injecting and sealing a liquid crystal 6 having negative dielectricconstant anisotropy in a cell that is provided by combining theabove-described TFT substrate 2 and opposite substrate 4.

When the liquid crystal display in the present embodiment is drivennormally, alignment division will be achieved as described below. In theregions where the comb-shaped electrodes 17 b are provided, liquidcrystal molecules are aligned in directions in which slits formed by thecomb-shaped electrodes 17 b extend. The remaining regions or the regionswhere the solid electrodes 17 a are formed, the liquid crystal isaligned toward the centers of the electrode units 17 because of obliqueelectric fields at the peripheries of the solid electrodes 17 a orliquid crystal orientation exerted from the outside by the comb-shapedelectrodes 17 b. Thus, alignment division in four general directions canbe achieved.

Embodiment 3-2

A liquid crystal display according to Embodiment 3-2 in the present modefor carrying out the invention will now be described. FIG. 34 shows aconfiguration of a pixel on a TFT substrate of the liquid crystaldisplay of the present embodiment. FIG. 35 shows a sectionalconfiguration of the liquid crystal display taken along the line K-K inFIG. 34. As shown in FIGS. 34 and 35, the liquid crystal display of thepresent embodiment is characterized in that there is no (orsubstantially no) region where a pixel electrode 16 and a reflector 53overlap each other, and the edge of an opening in a reflector 53 and theedge of a pixel electrode 16 are substantially aligned with each otherwhen viewed vertically to the surface of the substrate, unlikeEmbodiment 3-1. The edge of the pixel electrode 16 may be located insidethe edge of the opening in the reflector 53. The liquid crystal displayof the present embodiment is characterized in that an electrode unit 17is constituted only by a solid electrode 17 a and is formed with nocomb-shaped electrode 17 b.

In the liquid crystal display of the present embodiment, since liquidcrystal molecules in a reflective area R are driven by an obliqueelectric field at the edge of the pixel electrode 16, an effectivevoltage applied to a liquid crystal 6 during driving can be made smallerthan that applied to a transmissive area T. As a result, a voltage thatis optimal for display in the reflective mode can be applied to theliquid crystal 6 in the reflective area R, which makes it possible toachieve preferable display in the reflective mode.

Embodiment 3-3

A liquid crystal display according to Embodiment 3-3 in the present modefor carrying out the invention will now be described. FIG. 36 shows aconfiguration of a pixel on a TFT substrate of the liquid crystaldisplay of the present embodiment. FIG. 37 shows a sectionalconfiguration of the liquid crystal display taken along the line L-L inFIG. 36. As shown in FIGS. 36 and 37, in the present embodiment, only asolid electrode 17 a of an electrode unit 17 is formed in a transmissivearea T, and only comb-shaped electrodes 17 b of an electrode unit 17 areformed in a reflective area R.

In the liquid crystal display of the present embodiment, since liquidcrystal molecules in a reflective area R are driven by comb-shapedelectrodes 17 b, an effective voltage applied to a liquid crystal 6during driving can be made smaller than that applied to a transmissivearea T. As a result, a voltage that is optimal for display in thereflective mode can be applied to the liquid crystal 6 in the reflectivearea R, which makes it possible to achieve preferable display in thereflective mode.

A solid electrode 17 a and comb-shaped electrodes 17 b may be formed ina transmissive area T, and comb-shaped electrodes 17 b including linearelectrodes 17 d in a quantity smaller than that in the transmissive areaT may be formed in a reflective area R. Alternatively, each of gapsbetween adjoining comb-shaped electrodes 17 b in the reflective area R(the gaps between adjoining linear electrodes 17 d) may be made greaterthan each of gaps between adjoining comb-shaped electrodes 17 b in thetransmissive area T.

While electrode units 17 having a solid electrode 17 a and comb-shapedelectrodes 17 b have been referred to as examples in Embodiments 3-1 to3-3, electrode units 17 having no solid electrode 17 a may be used. Suchan electrode unit 17 has comb-shaped electrodes 17 b including aplurality of linear electrodes 17 d extending from a central section ofthe electrode unit 17 toward the periphery of the electrode unit 17. Inthis case again, the number of linear electrodes 17 d in a reflectivearea R may be smaller than the number of linear electrodes 17 d in atransmissive area T. Alternatively, each of gaps between adjoiningcomb-shaped electrodes 17 b in the reflective area R may be made greaterthan each of gaps between adjoining comb-shaped electrodes 17 b in thetransmissive area T.

Configurations of CF layers of a liquid crystal display in the presentmode for carrying out the invention will now be described. FIGS. 38A to39C show examples of configurations of CF layers of a liquid crystaldisplay in the present mode for carrying out the invention.

FIG. 38A shows a first example of a configuration of CF layers. As shownin FIG. 38A, CF layers 40R, 40G and 40B are formed only on an oppositesubstrate 4. In the present example, an insulating resin layer 36 isformed on a drain bus line 14 on a TFT substrate 2, and an Al thin filmis formed and patterned on the insulating resin layer 36 to form areflector 53. An insulating resin layer 37 is then formed on thereflector 53, and a pixel electrode 16 is formed on the insulating resinlayer 37. In this configuration, coloring in a transmissive area T and areflective area R is performed using the CF layers 40R, 40G and 40Bwhich constitute a single layer. When coloring in the transmissive areaT is properly performed, over-coloring may occur in the reflective areaR where light passes through the CF layers 40R, 40G and 40B twice.

FIG. 38B shows a second example of a configuration of CF layers. Asshown in FIG. 38B, in the present example, CF layers 41R, 41G and 41Bare provided on a drain bus line 14 on a TFT substrate 2. When the CFlayers 41R, 41G and 41B in different colors are formed in adjoiningpixels, the layers may be overlapped with some overlapping width. Thereason is that a reflector 53 is provided on a viewer's side of the CFlayers 41R, 41G and 41B, and the overlaps between the CF layers 41R, 41Gand 41B are therefore invisible during display in both of thetransmissive and reflective modes. After the CF layers 41R, 41G and 41Bare formed, the reflector 53 which is constituted by an Al thin film isformed on the gate bus line 12 and the drain bus line 14. An insulatingresin layer 37 made of a transparent resin is provided on the reflector53, and a pixel electrode 16 constituted by an ITO is provided on theinsulating resin layer 37. In the present example, since the reflector53 is formed on the viewer's side of the CF layers 41R, 41G and 41B, aconfiguration is achieved in which the CF layers 41R, 41G and 41B arepresent only in a transmissive area T and in which substantially none ofthe CF layers 41R, 41G and 41B is present in a reflective area R.Although this allows proper coloring for display in the transmissivemode, color purity may be reduced for display in the reflective mode.

FIG. 38C shows a third example of a configuration of CF layers. As shownin FIG. 38C, in the present example, CF layers 40R, 40G and 40B areprovided on an opposite substrate 4, and CF layers 41R, 41G and 41B areprovided on a TFT substrate 2. The configuration of the TFT substrate 2is similar to that in the second example, and the configuration of theopposite substrate 4 is similar to that in the first example. In atransmissive area T, coloring is performed by both of the CF layers 41R,41G and 41B on the TFT substrate 2 and the CF layers 40R, 40G and 40B onthe opposite substrate 4. In a reflective area R, coloring is performedonly by the CF layers 40R, 40G and 40G on the opposite substrate 4. Thatis, color characteristics suitable for both of the transmissive area Tand the reflective area R can be achieved by adjusting the thickness ofeach of the CF layers 40R, 40G and 40B and the CF layers 41R, 41G and41B.

FIG. 38D shows a fourth example of a configuration of CF layers. Asshown in 38D, in the present example, two layers comprising a set of CFlayers 40R, 40G and 40B and a set of CF layers 41R, 41G and 41B,respectively, are formed on a TFT substrate 2. CF layers 40R, 40G and40B having optical characteristics similar to those of the CF layers40R, 40G and 40B in the third example are provided above a reflector 54on the TFT substrate 2, which eliminates a need for forming CF layers onan opposite substrate 4. What is needed to be provided on the oppositesubstrate 4 is only a common electrode 42 (along with an alignmentcontrolling protrusion 44).

FIG. 39A shows a fifth example of a configuration of CF layers. As shownin FIG. 39A, in the present example, an insulating resin layer 37 isformed on CF layers 40R, 40G and 40B on a TFT substrate 2. As a result,since the CF layers will not be exposed on the surface of the TFTsubstrate 2, contamination of a liquid crystal layer 6 can be prevented.In this case, however, it is required to form three resin layersincluding two sets of CF layers on the TFT substrate 2.

FIG. 39B shows a sixth example of a configuration of CF layers. While areflector 53 is formed such that it is continuous between adjoiningpixels in the first through fifth examples, a reflector 53 is split toserve each pixel in this example as shown in FIG. 39B.

FIG. 39C shows a seventh example of a configuration of CF layers. Asshown in FIG. 39C, the present example is a modification of the firstexample, in which CF layers 40R, 40G and 40B on an opposite substrate 4are formed only in a transmissive area T. In a reflective area R whereno CF layer is formed, a transparent resin layer 38 having a thicknesssubstantially equal to or smaller than that of the CF layers 40R, 40Gand 40B is formed. Although this results in a reduction of color purityjust as in the second example during display in the reflective mode,luminance of reflection is conversely increased.

As described above, in the present mode for carrying out the invention,each of a transmissive area T and a reflective area R can be made toproperly work by providing them with different optical effects. Thismakes it possible to reduce a gradation difference between thetransmissive area T and the reflective area R. It is therefore possibleto provide a liquid crystal display which can achieve high displaycharacteristics in both of the reflective and transmissive modes.

Fourth Mode for Carrying Out the Invention

A liquid crystal display in a fourth mode for carrying out the inventionwill now be described with reference to FIGS. 40 to 46C.

A transflective liquid crystal display performs reflective displayutilizing external light in a bright environment and performstransmissive display utilizing light from a backlight in a darkenvironment to achieve display with high visibility in any environment.

FIG. 40 shows a sectional configuration of a transflective liquidcrystal display according to the related art which is disclosed inPatent Document 10. As shown in FIG. 40, in this liquid crystal display,a cell thickness in a reflective area R of a pixel region where areflective electrode 116 is formed is smaller than a cell thickness in atransmissive area T where a pixel electrode 117 is formed. An aligningunit for imparting at least two different aligning directions toalignment at an interface of a liquid crystal layer is provided in adisplay area of at least either of a pair of substrates. In thisconfiguration, since phase differences in the reflective area R and thetransmissive area T can be matched to each other, display can beperformed without color difference.

FIG. 41 shows a sectional configuration of a transflective liquidcrystal display according to the related art which is disclosed inPatent Document 11. In this liquid crystal display, a pixel electrode117 and a reflective electrode 116 are formed in a transmissive area Tand a reflective area R, respectively, on one substrate. A top surfaceof the reflective electrode 116 is formed like a series of waves. Inthis configuration, since the reflective area R can be provided withlight scattering power, high reflecting characteristics can be achieved.

However, the transflective liquid crystal display disclosed in PatentDocument 11 necessitates additional processes of forming an organicinsulation film 118 to make a cell thickness in the reflective area Rsmaller than a cell thickness in the transmissive area T and impartingat least two different aligning directions to alignment at an interfaceof a liquid crystal layer. Thus, steps for manufacturing a liquidcrystal display become complicated.

The transflective liquid crystal display disclosed in Patent Document 11also necessitates an additional process of forming protrusions 119 underthe reflective electrode 116 in order to form a series of wavyirregularities on the surface of the reflective electrode 116. Further,since the irregularities of the reflective electrode 116 functions asconductive protrusions when a voltage is applied, when used in avertical alignment type liquid crystal display in which the tiltingdirection of the liquid crystal is regulated using an alignmentcontrolling structure or dielectric structure formed on an electrode,the tilting direction of the liquid crystal determined by the protrusionwill be opposite to the tilting direction of the liquid crystaldetermined by an electric field, which will result in unstablealignment.

In the present mode for carrying out the invention, the above-describedproblems are solved, and a measure is taken to achieve a stable state ofalignment with a simple process even in a vertical alignment type liquidcrystal display.

FIG. 42 shows a first fundamental configuration of a liquid crystaldisplay in the present mode for carrying out the invention. As shown inFIG. 42, a liquid crystal layer 6 is sandwiched between a pair ofsubstrates 2 and 4. Liquid crystal molecules are vertically aligned whenno voltage is applied and are aligned at an inclination when a voltageis applied because of distortion of an electric field attributable toalignment controlling structures 44 and 46 formed on electrodes 16 and42. A reflector 54 having a smooth surface is formed in a part of apixel region. An alignment controlling structure 46 having lightscattering power is formed on the reflector 54.

More preferably, the reflector 54 is formed using a source (or drain)electrode layer or a gate electrode layer, and at least a pixelelectrode 16 is formed between the reflector 54 and the alignmentcontrolling structure 46. In addition, the alignment controllingstructure 46 is formed like a frame in the pixel region, and apoint-like alignment controlling structure 44 is formed in a region onthe opposite substrate 4 corresponding to the interior of the frame.

FIG. 43 shows a second fundamental configuration of a liquid crystaldisplay in the present mode for carrying out the invention. As shown inFIG. 43, liquid crystal molecules are vertically aligned when no voltageis applied and are aligned at an inclination when a voltage is appliedbecause of distortion of an electric field attributable to an alignmentcontrolling structure 44 and slits 48 formed on electrodes. A reflectivesheet (reflective section) 91 having a parallax correcting function isprovided behind a light guide plate 86. Irregularities on a surface ofthe reflective sheet 91 are formed at a pitch different from that ofpixel patterns.

More preferably, the irregularities on the surface of the reflectivesheet 91 have a sectional shape in the form of consecutive cones orwedges. A viewing angle control plate 96 for scattering light enteringat a predetermined angle is provided between a substrate 4 and apolarizer 71. In the present mode for carrying out the invention, aliquid crystal panel is sandwiched by a pair of ¼ wave plates 94 andpolarizers 70 and 71.

An alignment controlling structure 46 has a general sectional shape inthe form of an arc. Therefore, a reflective area R includes a regionwhere the cell thickness is equal to the cell thickness in atransmissive area T and a region where the cell thickness stepwisebecomes smaller than the cell thickness in the transmissive area T.However, since a voltage applied to the liquid crystal in the reflectivearea R is attenuated by the alignment controlling structure 46, it isanticipated that the combination of such regions provides an effectsubstantially similar to that achievable with a small cell thickness inthe reflective area R. Further, by providing the alignment controllingstructure 46 with light scattering power, incident light can bescattered in the reflective area R to achieve reflective display withhigh luminance. Since the surface of the reflector 54 can therefore beflat, the reflector 54 can be formed using a source electrode layer orgate electrode layer. Therefore, processes for manufacturing a liquidcrystal display can be simplified. When the pixel electrode (transparentelectrode) 16 is formed between the reflector 54 and the alignmentcontrolling structure 46, the reflective area R can be switched by thepixel electrode 16 without applying a voltage to the reflector 54. Inaddition, when the alignment regulating structure 46 is formed like aframe, a horizontal electric field generated between the bus lines 12and 14 and between the TFT 20 and the pixel electrode 16 can besuppressed to stabilize alignment of the liquid crystal in the pixelregion.

The alignment controlling structures 44 and 46 are aligning units forproviding different aligning directions. In the configuration disclosedin Patent Document 10, an alignment regulating force is imparted to aninterface of a liquid crystal layer using an interface aligning processsuch as rubbing. In the present mode for carrying out the invention, analignment regulating force is applied to the entire liquid crystal layerincluding a bulk layer utilizing distortions of electric fields thatoccur in the vicinity of the alignment controlling structures 44 and 46when a voltage is applied. Patent Document 10 discloses that the patentis characterized in that alignment of a liquid crystal in a reflectivearea R and alignment of the liquid crystal in a transmissive area T canbe in different states at the same point in time. Therefore, thealignment controlling structures 44 and 46 in the present mode forcarrying out the invention which allow different states of alignment inthe reflective area R or transmissive area T are different from thealigning process disclosed in Patent document 10.

When the reflective sheet 91 having a parallax correcting function isprovided under the light guide plate 86, reflective display can beperformed without providing the reflector 54 in the liquid crystaldisplay panel, and transmissive display can be achieved with highluminance because the utilization of pixel regions is maximized. Sincelight passes through the polarizers 70 and 71 four times duringreflective display, luminance per unit area will be lower than that in aconfiguration in which the reflector 54 is provided in a liquid crystaldisplay panel. However, luminance per pixel can be improved because theutilization of pixel regions can be maximized.

The reflective sheet 91 is provided with a parallax correcting functionbecause parallax (a double image) occurs because of the reflective layerbeing apart from the liquid crystal layer. Any interference occurringbetween the reflective sheet 91 and the pixel pattern can be suppressedby making the irregularities on the surface of the reflective sheet 91different from the pixel pattern. In addition, when the surfaceirregularities have a sectional shape in the form of consecutive cones,light entering in an oblique direction can be subjected toretroreflection. When the surface irregularities have a wedge-likesectional shape, light entering in an oblique direction can be obliquelyreflected out of the field of view. Thus, the occurrence of parallax canbe efficiently suppressed. By sandwiching the liquid crystal displaypanel with the pair of ¼ wave plates 94 and the polarizers 70 and 71,light which has entered the liquid crystal display panel can besubjected to circular polarization, which makes it possible to eliminateorientation-dependence of liquid crystal alignment and to achievereflective display and transmissive display with high luminance.

Liquid crystal displays in the present mode carrying out the inventionwill now be specifically described with reference to preferredembodiments.

Embodiment 4-1

First, a liquid crystal display according to Embodiment 4-1 in thepresent mode for carrying out the invention will be described. FIG. 44shows a configuration of a pixel of the liquid crystal display of thepresent embodiment. As shown in FIG. 44, a reflector 54 (not shown inFIG. 44) in the form of a frame was formed in the pixel region using agate electrode layer. A pixel electrode 16 made of transparentconducting layer is formed in the pixel region such that it overlaps thereflector 54 with a gate insulation film interposed between them. Thereflector 54 is in an electrically floating state and is electricallyinsulated from a gate bus line 12 and a storage capacitor bus line 18.While the pixel electrode 16 is overlaid on the reflector 54 with thegate insulation film interposed between them, in order to improvereflectivity, the pixel electrode may be formed like slits, for example,so that it overlaps only a part of the reflector 54. An alignmentcontrolling structure 46 in the form of a frame made of a white resinincluding alumina particles on a submicron order was formed in a regionon the pixel electrode 16 associated with the reflector 54. An alignmentcontrolling structure 46 in the form of a frame made of a transparentresin was fabricated for the purpose of comparison.

A common electrode 42 and a point-like alignment controlling structure44 made of a transparent resin were formed on an opposite substrate 4. Apair of ¼ wave plates 94 and polarizers 70 and 71 were provided outsidesubstrates 2 and 4 of the liquid crystal display panel, respectively. Alight guide plate 86 and a reflective sheet 90 were provided under thepolarizer 70 on the TFT substrate 2 to provide a transflective liquidcrystal display. A comparison of gradation characteristics of the liquidcrystal display during transmissive display and reflective displayrevealed no significant difference. This indicates the following fact.Even when a reflective area R includes a region where the cell thicknessis substantially equal to the cell thickness in a transmissive area Tand a region where the cell thickness stepwise becomes smaller than thecell thickness in the transmissive area T, if a voltage applied to theliquid crystal in the reflective area R is attenuated by the alignmentcontrolling structure 46, it is anticipated that the combination of suchregions provides an effect substantially similar to that achievable witha small cell thickness in the reflective area R.

When the alignment controlling structure 46 on the reflector 54 wasformed of a transparent resin, reflective display had low luminance indirections other than the direction of regular reflection. On thecontrary, when the alignment controlling structure 46 was formed of awhite resin, reflective display could be performed with high luminanceeven in directions other than the direction of regular reflection. Thisindicates that reflected light is scattered by light scattering power ofthe alignment controlling structure 46.

Embodiment 4-2

A liquid crystal display according to Embodiment 4-2 in the present modefor carrying out the invention will now be described. FIG. 45 shows aconfiguration of a pixel of the liquid crystal display of the presentembodiment. As shown in FIG. 45, in the present embodiment, a pixelelectrode 16 having slits 48 for controlling alignment was formed in thepixel region without forming a reflector 54 in the pixel region. Acommon electrode 42 and a point-like alignment controlling structure 44made of a transparent resin were formed on an opposite substrate 4. Apair of ¼ wave plates 94 and polarizers 70 and 71 were provided in theorder listed outside substrates 2 and 4 of the liquid crystal displaypanel. A light guide plate 86 and three types of reflective sheets 91 tobe described later were provided under the polarizer 70 on the TFTsubstrate 2. A viewing angle control plate 96 for scattering lightentering in a certain direction was provided between the polarizer 71and the ¼ wave plate 94 on the opposite substrate 4 to provide atransflective liquid crystal display. For comparison, a transflectiveliquid crystal display having no viewing angle control plate 96 and atransflective liquid crystal display having neither ¼ wave plate 94 norviewing angle control plate 96 were fabricated.

FIGS. 46A, 46B and 46C show sectional configurations of the three typesof reflective sheets 91. A reflective sheet 91 a shown in FIG. 46A has asmooth surface similarly to reflective sheets in the related art. Areflective sheet 91 b shown in FIG. 46B has a continuous conicalsectional shape and has a dimension equal to or smaller than a pixelpitch. A reflective sheet 91 c shown in FIG. 46C has a continuouswedge-like sectional shape and has a dimension equal to or smaller thanthe pixel pitch.

Reflected light from the reflective sheet 91 that is in a position apartfrom the liquid crystal layer has substantially no perceivable parallaxin a direction square to the display. In an oblique direction, however,a double image attributable to parallax occurs because of a greatdeviation of the reflecting position. In the case of the reflectivesheet 91 a, since incident light is subjected to regular reflection onthe surface thereof, a double image occurs when viewed in an obliquedirection. In the case of the reflective sheet 91 b, however, sinceincident light is subjected to retroreflection, substantially no doubleimage occurred. In the case of the reflective sheet 91 c, since incidentlight was reflected out of the field of view of a viewer, substantiallyno double image occurred. While the reflective sheet 91 b has acontinuous conical sectional shape with a dimension equal to or smallerthan the pixel pitch, it may have a plurality of corner cubes. Thereflective sheet 91 may be formed of a retroreflective material.

Although no adjustment of a phase difference is performed betweentransmissive display and reflective display in the present embodiment,similar gradation characteristics are achieved in both modes of displaywithout a phase difference adjustment because the reflective sheet 91serving as a reflective layer is provided outside the polarizer 70 toachieve similar polarizing characteristics during reflective display andtransmissive display. While reflective display had low luminance when noviewing angle control plate 96 was provided on the opposite substrate 4and when neither ¼ wave plate 94 nor viewing angle control plate 96 wasprovided, reflective display could be performed with high luminance evenin directions other than the direction of regular reflection when theviewing angle control plate 96 was provided on the opposite substrate 4.The luminance of reflective display was lowest when neither ¼ wave plate94 nor viewing angle control plate 96 was provided

The present mode for carrying out the invention makes it possible tomanufacture a transflective liquid crystal display having displaycharacteristics of both of reflective and transmissive types withsimplified processes. It is therefore possible to provide atransflective liquid crystal display at a low cost.

The invention is not limited to the above-described modes for carryingout the same and may be modified in various ways.

For example, while liquid crystal displays having CF layers formed on anopposite substrate 4 have been described as examples in the first andsecond modes for carrying out the invention, the invention is notlimited to them and may be applied to liquid crystal displays having aso-called CF-on-TFT structure in which CF layers are formed on a TFTsubstrate 2.

1. A liquid crystal display comprising: a pair of substrates opposite toeach other; a liquid crystal layer sealed between the pair ofsubstrates; and a pixel region having a reflective area including areflector for reflecting light entering from the side of one of the pairof substrates, the reflector being provided on the other of the pair ofsubstrates, and a transmissive area for transmitting light entering fromthe side of the other of the pair of substrates toward the one of thepair of substrates, wherein the reflector is provided at the peripheryof the pixel region; wherein the transmissive area has a transparentpixel electrode which is provided at an opening of the reflector andwhich is formed above the reflector and electrically isolated from thereflector; and wherein a cell thickness of the reflective area issubstantially equal to or greater than a cell thickness of thetransmissive area.
 2. A liquid crystal display according to claim 1,wherein the reflector is provided on a bus line formed on the other ofthe pair of substrates.
 3. A liquid crystal display according to claim1, wherein the reflector is in an electrically floating state.
 4. Aliquid crystal display according to claim 1, wherein the reflector is atthe same potential as that of a common electrode formed on either of thepair of substrates.
 5. A liquid crystal display according to claim 1,wherein the reflector is at a ground potential.
 6. A liquid crystaldisplay according to claim 1, wherein the reflector is formed such thatit is continuous between adjoining pixel regions.
 7. A liquid crystaldisplay according to claim 1, wherein the reflector is split betweenadjoining pixel regions.
 8. A liquid crystal display according to claim1, wherein the pixel electrode partially overlaps the reflector whenviewed perpendicularly to a substrate surface.
 9. A liquid crystaldisplay according to claim 1, wherein an edge of the pixel electrode isaligned with an edge of the opening of the reflector when viewedperpendicularly to the substrate surface.
 10. A liquid crystal displayaccording to claim 1, wherein the edge of the pixel electrode is locatedinside the edge of the opening of the reflector when viewedperpendicularly to the substrate surface.
 11. A liquid crystal displayaccording to claim 1, wherein the edge of the pixel electrode is locatedoutside the edge of the opening of the reflector when viewedperpendicularly to the substrate surface.
 12. A liquid crystal displayaccording to claim 1, wherein the pixel electrode includes a pluralityof electrode units which are provided adjacent to each other with slitsinterposed between them and which are electrically connected to eachother.
 13. A liquid crystal display according to claim 12, wherein thereflector is further formed on the slits.
 14. A liquid crystal displayaccording to claim 12, wherein each of the electrode units has a solidelectrode provided in a part of the electrode unit, and comb-shapedelectrodes including a plurality of linear electrodes extending from theperiphery of the solid electrode toward the periphery of the electrodeunit.
 15. A liquid crystal display according to claim 14, wherein thesolid electrode is formed in the transmissive area.
 16. A liquid crystaldisplay according to claim 14, wherein the comb-shaped electrodes areformed such that they extend into the reflective area.
 17. A liquidcrystal display according to claim 16, wherein the comb-shapedelectrodes in the reflective area include a smaller number of linearelectrodes than the comb-shaped electrodes in the transmissive area. 18.A liquid crystal display according to claim 16, wherein each of gapsbetween adjoining comb-shaped electrodes formed by the comb-shapedelectrodes in the reflective area is greater than each of gaps betweenadjoining comb-shaped electrodes formed by the comb-shaped electrodes inthe transmissive area.
 19. A liquid crystal display according to claim12, wherein each of the electrode units has comb-shaped electrodesincluding a plurality of linear electrodes extending from a centralsection of the electrode unit toward the periphery of the electrodeunit.
 20. A liquid crystal display according to claim 19, wherein eachof gaps between adjoining comb-shaped electrodes formed by thecomb-shaped electrodes in the reflective area of the electrode unit isgreater than each of gaps between adjoining comb-shaped electrodesformed by the comb-shaped electrodes in the transmissive area.
 21. Aliquid crystal display according to claim 19, wherein the comb-shapedelectrodes in the reflective area of the electrode unit include asmaller number of linear electrodes than the comb-shaped electrodes inthe transmissive area.
 22. A liquid crystal display according to claim12, wherein either of the pair of substrates has a protrusion forcontrolling alignment in a region associated with the central section ofthe electrode unit.
 23. A liquid crystal display according to claim 1,further comprising a color filter layer formed under the reflector. 24.A liquid crystal display according to claim 23, further comprising asecond color filter layer formed on either of the pair of substrates.25. A liquid crystal display according to claim 23, further comprising asecond color filter layer formed above the reflector.
 26. A liquidcrystal display according to claim 1, further comprising a color filterlayer formed on either of the pair of substrates, wherein the colorfilter layer is removed in the reflective area.
 27. A liquid crystaldisplay according to claim 26, wherein the reflective area has atransparent resin layer having a thickness substantially equal to orsmaller than the thickness of the color filter layer.
 28. A liquidcrystal display according to claim 1, comprising a pair of ¼ wave platesand a pair of polarizers provided outside the pair of substrates,respectively.
 29. A liquid crystal display according to claim 1,comprising a light scattering layer formed outside either of the pair ofsubstrates.
 30. A liquid crystal display according to claim 29, whereinthe light scattering layer is a film which scatters light entering in apredetermined direction.